Currently, maintenance in electric power distribution networks may be carried out in medium or low voltage networks, on energized or non-energized lines, being the later a more recommended procedure, because all maintenance activities in the power sector must give priority to services with non-energized power lines, and power lines are considered to be non-energized when cleared for service based on appropriate protocols. It is important to highlight that services with non-energized power lines also requires safety procedures and measures to be in place, pursuant to regulations or recommendations, and the adoption of the necessary procedures, methodologies and tools for each one of the situations described.
Until some time ago, maintenance on non-energized power lines was considered safe by electricians; however, because of the increased number of circuits and more complex distribution networks, as well as incidents and fatal accidents, deenergizing lines was no longer safe enough, especially due to the risk of accidental energization.
Pursuant to NR-18 Regulation, when it is not possible to turn off the electric circuit, services performed in energized power lines is only possible once additional protection measures have been implemented, being mandatory to use appropriate tools and personal protective equipment as set forth in NR-10 Regulation, which are adequate to each voltage range, in addition to implementing procedures and methodologies to ensure workers safety.
Tree pruning means removing certain parts of the plant to avoid interference with BT or MT/AT networks, thus avoiding short circuit among conductors. Tree pruning may be carried out for several reasons, including to maintain or improve tree health, and to ensure the safety and reliability of power systems and people. However, when tree pruning is carried out by electric power companies, operators should not only prune specific parts of the tree that may jeopardize the integrity of distribution lines, but also ensure the tree will not lose its stability and eventually fall down or die.
Managing city plants and trees, including planning, planting, maintaining and preserving trees, is under the responsibility of the local government. Nevertheless, electric power companies must prune trees whenever the operation of electric power distribution networks is threatened. This task should be performed by a pruner specialized in power networks, who is duly trained to handle trees and plants near electric power lines.
It is important to highlight that trees located near electrical conductors in different points of electric power distribution networks are the major cause of aerial electric power distribution network failure, i.e. broken electrical conductors, light poles falling down, fatigue of accessories, and power failure. Increased tree pruning leads to fewer interruptions in the electric power distribution system. The cost of tree pruning, to ensure reliability of electric power distribution networks, represents a great part of the total costs incurred annually by power companies with network servicing.
Furthermore, tree pruning has several risks, it is a dangerous task, especially to power company operators or their service providers working around aerial power lines in general, including working at height, risk of electric shock, risk of falls, accidents involving pruning tools, and insect attacks. This high risk profile for workers encourages the constant development and design of devices that can make such tasks safer and more comfortable.
According to the technical procedures adopted by power companies, tree pruning near multiplexed power lines, either of primary or secondary voltage, is only justified if tree branches or the tree itself is causing mechanical problems to the conductors. This is because in multiplexed networks, conductors can be touched by tree branches nearby. For compact distribution networks, the same precautions must be taken and the same safety distance from the network must be kept, as these networks are protected only, but not isolated.
Currently, tree pruning is carried out by power companies or their service providers as follows: branches located below conductors and which are invading the minimum safety distance from high voltage primary networks, either conventional or compact ones, are removed. This is carried out by non-energized line operators who generally use mechanical tools or combustion chainsaws, and truck-mounted ladders or regular ladders; branches growing from bottom to top towards the network must be pruned provided that they are not touching the conductors. This is carried out by non-energized line operators who generally use mechanical tools or combustion chainsaws, and truck-mounted ladders or regular ladders; branches located over the primary network and touching conductors can only be pruned if the line has been deenergized, tested, grounded and tagged out, or by energized line operators who are trained to perform this kind of service and who use all necessary PPE and CPE.
Some steps have to be taken during tree pruning near electric power distribution networks: preliminary procedures; tree pruning; and subsequent procedures. Additionally, other procedures are necessary in specific situations or when using shredders and truck-mounted containers.
Currently, tree pruning procedures widely known by the current state of the art are based on manual hydraulic-type or combustion-type pruning tools, which must have electrical isolation to avoid risks to electricians. The tools used include: hand pruners for smaller branches; pole pruners (variable length) activated by a rope for high branches; manual saws for thicker branches with the following main characteristics: blade angle, number of teeth, rigidity, blade profiling, and cutting direction; and fixed-support chainsaws adapted to tree pruning in city environments with the following main characteristics: cutting heads, type of activation, and pole. For larger branches, the chainsaw must be supported by a specific auxiliary rope.
In this context, robotics can be applied successfully to the power sector. In fact, robots have been used to replace human labour in some and repetitive tasks, which pose a risk to operator safety due to the inherent characteristics of the process, or tasks that must be carried out in dangerous locations. Therefore, the power sector has a wide range of elements where robotics can be used, including electric power network maintenance or inspection, and, more specifically, it may help to significantly increase productivity and offer a safe environment for task execution.
Other factors that foster the use of robotics in power systems include cost reduction, as fewer specialized operators are used in the task, and task reproducibility assurance when robotic devices are automated.
Due to the risks associated with tree pruning and the importance of this activity for the good operation of aerial distribution networks, power companies, especially their service providers working with tree pruning near conductors in electric power distribution networks, urgently need a versatile, convenient, safe and precise piece of equipment to streamline tree pruning tasks near conductors to be carried out by power companies themselves or their service providers.
In an extensive literature review, conducted to define the current state of the art regarding tree pruning equipment near energized inner-cities, object of this invention, no relevant documents to the state of the art were found that relate to the specific equipment claimed in this invention, i.e. proper solutions for tree pruning near energized inner-cities, more specifically, a robotic equipment remote-controlled by an operator for tree pruning near energized inner-cities based on an isolated teleoperated mechanical arm containing tools adapted as end effectors, integrated to shredding devices and a collection bin for the tree branches removed after pruning.
Therefore, this patent gathers components and processes in a distinguished invention, which will meet the different demands of the task, i.e. tree pruning and branch shredding near energized power lines in urban areas. This invention will offer a remote-controlled robotic equipment which is highly efficient, functional, resistant, durable, safe, versatile, precise, and ergonomic in the light of its excellent technical features, and which will offer advantages and improve tree pruning procedures near conductors in electric power lines performed by power company operators or service providers, and whose general characteristics are different from other forms and models known by the current state of the art.
What is needed therefore, is an equipment intended for use in electric power distribution networks in general, more specifically a remote-controlled robotic equipment for tree pruning near energized power lines whose basic principle, according to its general characteristics, is to provide a remote-controlled robotic equipment in its own, a specific electromechanical structure coupled to a truck and based on a robotic arm with a stand, a positioner, a handler and an end effector-pruning tool, a collection bin and a tree branch shredder, all of which are integrated, for robotized tree pruning near energized power lines, which can conveniently, safely and precisely streamline the procedures adopted in the maintenance of aerial electric power distribution networks, more specifically, tree pruning near urban electric power distribution networks, combined with full ergonomics and no exposure of operators to these routine procedures and based on a remote-controlled robotic equipment with great resistance, safety and versatility. Specifically designed and shaped, and easily accessible for better adaptation and safety for users, convenient handling and functionality due to its general characteristics and sizing, easily usable in a wide range of tree pruning situations involving urban electric power lines, including power lines of any construction type in the field of engineering, both low, medium and high voltage networks, in general.